This invention relates to a pulse oximetry sensor and more particularly to a lead frame for an integrated pulse oximetry sensor.
It is common in medical practice to measure pulse rate and oxygen saturation in blood. Pulse oximetry uses discrete wavelengths of light to measure the optical density of hemoglobin. Pulse oximetry can also distinguish arterial blood from venous blood and tissue.
Pulse oximeters are used extensively in critical care areas of hospitals to monitor a patient's arterial % oxygen saturation (S.sub.p O.sub.2) and pulse rate (PR). The pulse oximetry instrument records the absorption of light in perfused tissue at two or more wavelengths. The instrument computes S.sub.p O.sub.2 and PR by comparing the time variant and time invarient portions of the light absorption signal. The history and technology of oximetry is well known in the art and it is thoroughly discussed in chapter 16 of Monitoring in Anesthesia and Critical Care Medicine which is edited by C. D. Blitt M.D., the teachings of which are incorporated herein by reference.
The preferred site for a pulse oximetry sensor is a finger tip, although other sites are commonly used. The sensor must incorporate light sources, a photodetector, means for mechanically orienting the components relative to the tissue and means for energizing the light sources and returning the optical signals to the pulse oximetry instrument. The sensor must also incorporate means for mechanical attachment to the perfused tissue.
While there are several sensors currently in use, these sensors have several shortcomings. In some cases the sensors have too great a mass and therefore a significant motion artifact is developed when the sensor is in use. Other known sensors conform to the perfused tissue by applying a compressive force and in some cases the compressive force, while sufficient to secure the sensor to the profuse tissue, induces vascular shut down.
It is therefore a principal object of the present invention to provide an integrated lead frame pulse oximetry sensor that can be mechanically attached to perfused tissue yet is of a very low mass.
Another object of the present invention is to provide an integrated lead frame pulse oximetry sensor which can be mechanically attached to perfused tissue without applying compressive forces thereby avoiding vascular shut down.
Still another object of the present invention is to provide an integrated lead frame pulse oximetry sensor which can be manufactured at a cost that is low compared to other known sensors.